I honestly know very little about the PS2 hardware but it is my understanding that the 4MB of vram is similar to the eDRAM on the 360. It is there just for rendering to, and then must be copied to system memory before being read or used as video output. So when rendering an image that will not fit in this vram, you must tile it, where you render pieces of it and resolve each piece back to system memory. According to wikipedia the max resolution supported internally by the Graphics Synthesizer is 1280x1024. So they may have just rendered high res but not full 1080i. I have heard rumor that the ps2 could render interlaced fields which would cut the memory in half. Most consoles have to render the full resolution image even if the output is interlaced. Each interlaced field has half the vertical resolution so they could be cutting the memory requirements in half.
So my (not so educated) guess is they rendered well less than the full 1920x1080 needed for 1080i and instead just rendered as high as the ps2 allowed, in a tiled manner, and converted the image to a 1080i signal.
oops you are right but the numbers come out about the same. 1920x1080 pixels x4Bytes(8 bit per component) makes a 7.9MB buffer. The PS3 must store both its back buffer and z buffer in its local video memory making the two buffers 15.8meg. Then as you pointed out you also need a front buffer which is anothe 8MB. (total of roughly 24MB of your 256MB local video memory dedicated to the most basic buffers).
On the xbox360 it takes up less space. The Zbuffer never needs to be in memory since it exists on the eDRAM. So the buffers would take up 16MB of the available 512MB.
Bandwidth considerations are the same since i forgot to figure in the bandwidth for writing to the z-buffer as well.
I have serious doubts that true 1080p is really practical in this generation of consoles. The reason being, the more resolution you push the higher the bandwidth and the higher the memory cost. I think developers that produce 1080p games will really be producing 720p games and letting the console up-sample. And that ultimately does little for quality. Lets look as some numbers
On a console running at 1080p you have 1920x1080 pixels x8 bits (for non floating point HDR) That means 15.8 meg per frame buffer. A game typically has multiple buffers it renders to (especially for post processing effects) so there is almost 32meg consumed just so you can display an image. If you are using true floating point HDR one of those buffers would be 32meg.
If you are rendering at 720p a frame buffer is 7 meg for 8bit and 14 for 32bit float HDR.
There is also an impact on fill rate. The 1080p requires more than twice the fill rate. That means (when fill-rate bound) the frame rate must be cut in half or the effects being used must be reduces.
On the PS3 with a practical fill rate of 15GB/s to local video memory, you can overdraw a 1080p scene at 60fps only 16 times. That has a serious impact on use of particle effects, multi-pass rendering, and post processing. At 720p that overdraw rate increases to 36 times.
On an xbox360 the eDRAM affords a greater fill rate (64GB/s) so it could better handle the demands of 1080p but it has to contend with the 10Meg limit on the eDRAM. This means a 1080p scene would require a 4 pass tiled rendering and a 2 pass for scene post processing.
So basically I don't think we will even see true 1080p games without those games reducing their visuals significantly. I would rather have a slick looking 720p at 60fps than a 1080p that looks last generation.
Exactly. Not to say that Microsoft would do it right if they bundled all that functionality with the OS, but Apple has a competitive advantage by strictly controlling the hardware and being able to include anything it wants in an OS without the threat of an Anti-trust case. Microsoft could never do the stuff Apple does. Just look at iTunes; if Microsoft had a proprietary compression format that only they could use, and had 90% of the market i think it would be viewed as anti-competitive.
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unfortunalely the lasers used actually cause skin cancer in the process
I honestly know very little about the PS2 hardware but it is my understanding that the 4MB of vram is similar to the eDRAM on the 360. It is there just for rendering to, and then must be copied to system memory before being read or used as video output. So when rendering an image that will not fit in this vram, you must tile it, where you render pieces of it and resolve each piece back to system memory. According to wikipedia the max resolution supported internally by the Graphics Synthesizer is 1280x1024. So they may have just rendered high res but not full 1080i. I have heard rumor that the ps2 could render interlaced fields which would cut the memory in half. Most consoles have to render the full resolution image even if the output is interlaced. Each interlaced field has half the vertical resolution so they could be cutting the memory requirements in half.
So my (not so educated) guess is they rendered well less than the full 1920x1080 needed for 1080i and instead just rendered as high as the ps2 allowed, in a tiled manner, and converted the image to a 1080i signal.
my bad... 32bit color display, 8bit per component, and i beleive it is the same on all consoles.
oops you are right but the numbers come out about the same. 1920x1080 pixels x4Bytes(8 bit per component) makes a 7.9MB buffer. The PS3 must store both its back buffer and z buffer in its local video memory making the two buffers 15.8meg. Then as you pointed out you also need a front buffer which is anothe 8MB. (total of roughly 24MB of your 256MB local video memory dedicated to the most basic buffers).
On the xbox360 it takes up less space. The Zbuffer never needs to be in memory since it exists on the eDRAM. So the buffers would take up 16MB of the available 512MB.
Bandwidth considerations are the same since i forgot to figure in the bandwidth for writing to the z-buffer as well.
I have serious doubts that true 1080p is really practical in this generation of consoles. The reason being, the more resolution you push the higher the bandwidth and the higher the memory cost. I think developers that produce 1080p games will really be producing 720p games and letting the console up-sample. And that ultimately does little for quality. Lets look as some numbers
On a console running at 1080p you have 1920x1080 pixels x8 bits (for non floating point HDR) That means 15.8 meg per frame buffer. A game typically has multiple buffers it renders to (especially for post processing effects) so there is almost 32meg consumed just so you can display an image. If you are using true floating point HDR one of those buffers would be 32meg.
If you are rendering at 720p a frame buffer is 7 meg for 8bit and 14 for 32bit float HDR.
There is also an impact on fill rate. The 1080p requires more than twice the fill rate. That means (when fill-rate bound) the frame rate must be cut in half or the effects being used must be reduces.
On the PS3 with a practical fill rate of 15GB/s to local video memory, you can overdraw a 1080p scene at 60fps only 16 times. That has a serious impact on use of particle effects, multi-pass rendering, and post processing. At 720p that overdraw rate increases to 36 times.
On an xbox360 the eDRAM affords a greater fill rate (64GB/s) so it could better handle the demands of 1080p but it has to contend with the 10Meg limit on the eDRAM. This means a 1080p scene would require a 4 pass tiled rendering and a 2 pass for scene post processing.
So basically I don't think we will even see true 1080p games without those games reducing their visuals significantly. I would rather have a slick looking 720p at 60fps than a 1080p that looks last generation.
Exactly. Not to say that Microsoft would do it right if they bundled all that functionality with the OS, but Apple has a competitive advantage by strictly controlling the hardware and being able to include anything it wants in an OS without the threat of an Anti-trust case. Microsoft could never do the stuff Apple does. Just look at iTunes; if Microsoft had a proprietary compression format that only they could use, and had 90% of the market i think it would be viewed as anti-competitive.